In many industrial and manufacturing applications it is necessary to couple the ends of two fluid-handling conduits to effect a fluid-tight coupling therebetween, and accordingly a host of coupling devices have been developed for the purpose. Many of these coupling devices rely on metal band clamps tightened about a sleeve which is slipped over the ends of the conduits so that the sleeve is inwardly compressed against the conduits. Where the fluid within the conduits is under significantly higher pressure than ambient, some provision must be made for preventing the sleeve from "ballooning" outward and possibly failing or causing the sleeve to slip out from under the clamps. Thus, in some coupling devices a single metal band clamp is used which extends continuously over the joint between the two conduits and is tightened at its two ends about the conduits, for example as shown in U.S. Pat. Nos. 4,101,151 and 3,836,182.
In other types of coupling devices, the sleeve itself is made relatively stiff and rigid so as to resist ballooning. For example, in fluid systems for some aircraft, a coupling device sometimes used comprises a sleeve formed of multilayered fiberglass coated with silicone elastomer. The sleeve is sized to fit over the ends of the conduits to be joined and is secured by metal band clamps or the like. A difficulty associated with such coupling devices is that the stiff sleeve is frequently not able to adequately conform to the exterior contour of the conduit to form a reliable seal. For instance, misaligned conduits are difficult to seal with the stiff sleeve because the sleeve is not readily bendable. Sealing difficulties can also be encountered when the interface surface of the conduit is not smooth or has become dented or scratched, when the conduit is sized slightly larger or smaller than nominal, or when the conduit has become otherwise misshapen. If any of the aforementioned circumstances occur, leaks can develop. Thus, where the conduits are misaligned, a worker frequently must rework the conduits to bring them into alignment prior to installing the coupling device. Where the conduits are not smooth or are scratched or dented, a worker must polish and/or fill the surface of the misshapen conduit to provide a smooth surface for the sleeve to seal against. However, such procedures are labor-intensive and time-consuming. Leaks can also develop when relative movement occurs between the two conduits that are joined, because the stiff sleeve does not have enough "give" to compensate for the movement. The usual solution to leaks is to further tighten the clamps, but overtightening the clamps can cause damage to the conduit and/or to the sleeve, leading to potential loss of pressure. The consequences of the pressure loss can include loss of passenger comfort, loss of system performance, damage to or failure of a component, etc.
The coupling device employing the stiff fiberglass/elastomer sleeve also requires a separate wrap of insulation around the joint to prevent thermal and acoustics loss. The insulation typically comprises moisture-resistant insulation batting wrapped with fiber-reinforced perforated plastic film that is heat sealed, stitched, or taped in place. This method of assembly is expensive, labor-intensive, heavy, and unreliable. Moreover, the insulation typically requires periodic replacement if the plastic film becomes torn, if the insulating performance degrades as a result of shifting of the batting and/or repeated wetting and drying of the batting, or if the tape used to secure the plastic film fails or becomes loose because of age.
Thus, it would be desirable to provide a coupling device which has thermal and acoustical insulating functions without the necessity of wrapping a joint with insulation as in existing coupling devices employing stiff sleeves, and which does not degrade in insulating performance as a result of wetting, shifting insulation, or the like. It would also be desirable to provide a coupling device able to satisfactorily seal against scratched or dented conduits, conduits that are slightly larger or smaller than nominal, or conduits that are misshapen, so that reworking of the conduits can be avoided. Additionally, particularly in aircraft applications where a substantial number of coupling devices may be used in a single aircraft, it would be desirable to provide a coupling device having lower cost and lighter weight than existing coupling devices incorporating stiff sleeves and metal clamps and separate insulation materials.